Experiments in Fluids最新文献_第6页

Vibrational temperature measurement of diatomic nitrogen using femtosecond/picosecond coherent anti-Stokes Raman scattering in the ONR-UTA arc-jet facility ONR-UTA电弧喷射装置中飞秒/皮秒相干反斯托克斯拉曼散射双原子氮的振动温度测量

IF 2.7 3区工程技术

Experiments in Fluids Pub Date : 2026-07-31 DOI: 10.1007/s00348-026-04279-y

Ian Raybon, Luca Maddalena, Laura E. Dogariu, Arthur Dogariu

{"title":"Vibrational temperature measurement of diatomic nitrogen using femtosecond/picosecond coherent anti-Stokes Raman scattering in the ONR-UTA arc-jet facility","authors":"Ian Raybon, Luca Maddalena, Laura E. Dogariu, Arthur Dogariu","doi":"10.1007/s00348-026-04279-y","DOIUrl":"10.1007/s00348-026-04279-y","url":null,"abstract":"<div><p>Laser-based flow diagnostics offer significant advantages over classical probe-based intrusive instruments in regard to measurement capabilities, spatial and temporal resolution, and measurement uncertainty reduction. Due to the complex thermochemical nature of the gas exiting an arc-jet nozzle, direct experimental measurements of chemical and thermodynamic gas properties are required to accurately measure the flow enthalpy, understand test material response, and verify theoretical predictions. The presented work documents the first application of hybrid femtosecond/picosecond Coherent Anti-Stokes Raman Scattering (fs/ps-CARS) spectroscopy to non-equilibrium thermometry measurements in an arc-jet flow. Vibrational fs/ps-CARS spectroscopy in nitrogen freestream flow enabled thermodynamic measurements by fitting the spectra to a theoretical model of non-equilibrium fs/ps-CARS. Calibration measurements were used to adjust model parameters, capture the nonresonant background effects, and optimize experimental parameters for application in arc-heated Mach 4 nitrogen flow. With a strategy to limit the background radiation and address the challenges posed by the long optical paths, inherent to this class of arc-jet facilities, the measured vibrational and rotational temperatures of diatomic nitrogen were 3690 ± 87 K and 1370 ± 109 K, respectively, successfully capturing the thermochemical non-equilibrium state of the flow, and matching theoretical predictions. This demonstration lays the foundation for broadening the applicability of hybrid CARS to thermometry from other molecular flow constituents (e.g., O<span>(_2)</span>, NO), performing simultaneous rotational and vibrational measurements, and integrating with other ultra-fast optical diagnostics for a more comprehensive flow characterization.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 9","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-026-04279-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148628595","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Vortex–vortex interactions in lined double-slit cavities under combined tangential flow and acoustic excitation 切向流与声激励联合作用下双狭缝腔内涡-涡相互作用

IF 2.7 3区工程技术

Experiments in Fluids Pub Date : 2026-07-31 DOI: 10.1007/s00348-026-04281-4

Yuchao Tang, Peng Wang, Yingzheng Liu

{"title":"Vortex–vortex interactions in lined double-slit cavities under combined tangential flow and acoustic excitation","authors":"Yuchao Tang, Peng Wang, Yingzheng Liu","doi":"10.1007/s00348-026-04281-4","DOIUrl":"10.1007/s00348-026-04281-4","url":null,"abstract":"<div><p>This research provides experimental insights into the interactions between vortices in lined double-slit cavities, under simultaneous tangential flow and acoustic excitation. Notably, at high sound pressure levels, noise reduction is governed by the conversion of acoustic energy into vortical kinetic energy and its subsequent dissipation; this work therefore focuses on how the intensity of the tangential flow modulates the acoustic response and vortex–vortex interactions. To achieve synchronous measurement of acoustic responses, pressure fluctuations, and unsteady flow behavior, an integrated setup incorporating microphone arrays, pressure transducers, and particle image velocimetry (PIV) was implemented. The PIV system was synchronized via a field-programmable gate array (FPGA), ensuring precise phase-locked measurements through its real-time computing capability. Analysis of the transmission loss demonstrates that the double-slit configuration yielded greater acoustic attenuation compared to a single-slit geometry. This performance enhancement was found to be more pronounced under conditions of strong flow-convection effects. Subsequently, a comparative analysis was performed to examine the vortex dynamics under both weak and strong flow-convection effects. Under weak flow-convection effects, the separated vortex was primarily transported downstream, while under strong effects, the vortex system merged with the shear layer. Furthermore, the mechanism of acoustic-to-flow energy conversion was investigated through an analysis of pressure pulsations and identified coherent structures. The results revealed that the tangential flow significantly modulates the vortex–vortex interactions, as evidenced by a clear shift in the dominant mode from the interaction of separated vortices to the interaction within the internal cavity vortex system.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 9","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148628597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

On the characteristics of three-dimensional turbulent structures and wall-pressure fluctuations around finlet treatments 三维紊流结构特性及小波处理前后壁面压力波动

IF 2.7 3区工程技术

Experiments in Fluids Pub Date : 2026-07-31 DOI: 10.1007/s00348-026-04287-y

Zhihang Pan, Qingqing Ye

{"title":"On the characteristics of three-dimensional turbulent structures and wall-pressure fluctuations around finlet treatments","authors":"Zhihang Pan, Qingqing Ye","doi":"10.1007/s00348-026-04287-y","DOIUrl":"10.1007/s00348-026-04287-y","url":null,"abstract":"<div><p>This study experimentally investigates the impact of streamwise finlet height on the three-dimensional turbulent structures and wall-pressure fluctuations over a NACA0018 airfoil. The presence of finlets of three heights all induces two pairs of counter-rotating streamwise vortices, leading to a pronounced lifting effect behind them, followed by a recovery process downstream. The intensity of this lifting effect strongly depends on the finlet height. Short finlets convey the original streak structures upward, maintaining a spatial distance from the wall. Differently, the medium-height and tall finlets disrupt the streamwise velocity streaks in the turbulent boundary layer and generate new hairpin-like vortices in the detached shear layer. The stronger lifting effect displaces turbulent structures away from the wall, leading to a significant reduction in Reynolds shear stress and pressure fluctuations in the mid- and high-frequency bands. The best pressure reduction performance is obtained for median-height finlets. Excessively tall finlets introduce additional turbulent structures, thereby elevating low-frequency wall-pressure fluctuations and compromising high-frequency suppression.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 9","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148628598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Particle-enhanced temperature-sensitive paint: development and validation for high-speed aerothermodynamic testing 颗粒增强型温敏涂料：用于高速空气热力学测试的开发和验证

IF 2.7 3区工程技术

Experiments in Fluids Pub Date : 2026-07-31 DOI: 10.1007/s00348-026-04282-3

Jinyoung Kim, Mithat Engin, Masaki Okawa, Tsubasa Ikami, Bok Jik Lee, Hiroki Nagai

{"title":"Particle-enhanced temperature-sensitive paint: development and validation for high-speed aerothermodynamic testing","authors":"Jinyoung Kim, Mithat Engin, Masaki Okawa, Tsubasa Ikami, Bok Jik Lee, Hiroki Nagai","doi":"10.1007/s00348-026-04282-3","DOIUrl":"10.1007/s00348-026-04282-3","url":null,"abstract":"<div><p>Accurate surface temperature and heat flux measurements are essential for evaluating aerothermal loads on high-speed vehicles, including atmospheric entry capsules and space exploration vehicles. Temperature-sensitive paint provides a non-intrusive approach for global heat flux measurement in impulse ground-testing facilities, but its application is often limited by low signal levels caused by short test durations, high-frame-rate imaging, and the associated short exposure times. In this study, a particle-enhanced temperature-sensitive paint was developed and optimized by incorporating calcium silicate microparticles to improve luminescence output and measurement precision. Characterization tests showed that the optimized formulation increased emission intensity by 21% and temperature sensitivity by 11% relative to the reference temperature-sensitive paint, while retaining nearly twice the normalized emission intensity at 500 kPa. Shock tube validation demonstrated that the enhanced signal level reduced the standard deviation of reconstructed heat flux measurements by up to 33% under short-duration transient conditions, indicating the potential applicability of the particle-enhanced formulation for high-speed aerothermodynamic diagnostics.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 9","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-026-04282-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148628593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Helium-filled soap bubbles as flow tracer particles: a review 充氦肥皂泡作为流动示踪粒子：综述

IF 2.7 3区工程技术

Experiments in Fluids Pub Date : 2026-07-29 DOI: 10.1007/s00348-026-04278-z

Mahyar Moaven, Douglas W. Carter

引用次数: 0

Similarity criteria for ascending toroidal bubbles in water 水中上升环形气泡的相似准则

IF 2.7 3区工程技术

Experiments in Fluids Pub Date : 2026-07-29 DOI: 10.1007/s00348-026-04280-5

Viktor Nikulin, Evgeny Chashnikov

引用次数: 0

Experimental characterization and analysis of unsteady normal-shock boundary-layer interaction 非定常正激波边界层相互作用的实验表征与分析

IF 2.7 3区工程技术

Experiments in Fluids Pub Date : 2026-07-29 DOI: 10.1007/s00348-026-04269-0

Carmen Riveiro Moreno, Marie Couliou, Nicolò Fabbiane, Reynald Bur, Olivier Marquet

{"title":"Experimental characterization and analysis of unsteady normal-shock boundary-layer interaction","authors":"Carmen Riveiro Moreno, Marie Couliou, Nicolò Fabbiane, Reynald Bur, Olivier Marquet","doi":"10.1007/s00348-026-04269-0","DOIUrl":"10.1007/s00348-026-04269-0","url":null,"abstract":"<p>This study experimentally investigates the interaction of a normal shock wave and the turbulent boundary layer at an upstream Mach number of 1.35 in the transonic wind tunnel S8Ch at ONERA Meudon. Wall-mounted unsteady pressure measurements and high-speed schlieren imaging were combined to measure the shock–boundary layer interaction (SBLI). A small separation region was observed along the centerline. Spectral analysis of the reconstructed wall pressure signals revealed distinct frequency ranges associated with different flow features: shock wave (<span>(Stsim 0.01)</span>, peaking at <span>(Stapprox 0.013)</span>), separation point (<span>(Stapprox 0.04 - 0.25)</span>), and mixing layer (<span>(St > rsim 0.3)</span>). It was observed that in the separation region, time scales associated to the shock motion and mixing layer coexist. Spectral Proper Orthogonal Decomposition (SPOD) of schlieren images revealed coherent structures within the shear layer as well as low-frequency unsteadiness linked to the shock motion. Finally, synthetic image analysis showed that sharp discontinuities such as shocks can introduce additional modes at higher harmonics, highlighting the importance of careful interpretation in SBLI studies.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 9","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-026-04269-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148614792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Simultaneous free-surface profilometry and subsurface velocimetry with fringe projection and PIV 同时使用条纹投影和PIV的自由表面轮廓和地下速度测量

IF 2.7 3区工程技术

Experiments in Fluids Pub Date : 2026-07-28 DOI: 10.1007/s00348-026-04242-x

Ali Semati, Adharsh Shankaran, Benjamin K. Smeltzer, Eirik Æsøy, R. Jason Hearst, Simen Å. Ellingsen

{"title":"Simultaneous free-surface profilometry and subsurface velocimetry with fringe projection and PIV","authors":"Ali Semati, Adharsh Shankaran, Benjamin K. Smeltzer, Eirik Æsøy, R. Jason Hearst, Simen Å. Ellingsen","doi":"10.1007/s00348-026-04242-x","DOIUrl":"10.1007/s00348-026-04242-x","url":null,"abstract":"<div><p>This work presents a novel combination of two well-established techniques: fringe projection profilometry (FPP) and particle image velocimetry (PIV). Despite seemingly conflicting requirements—FPP requires an opaque surface to project onto, while PIV requires a transparent fluid—both requirements are met by adding low concentrations (4–25 mg/L) of fluorescein dye to the water. This dye strongly absorbs the blue light projected onto the surface for FPP while remaining nearly transparent to the green PIV laser, achieving simultaneous opacity and transparency depending on wavelength. A set of three optical filters suppresses fluorescence-induced noise in the PIV images and specular reflections in the profilometry images, enabling clean simultaneous acquisition. Validated against point laser-induced fluorescence measurements of the surface, the method achieves a mean absolute error in surface elevation of 18 <span>(upmu text {m})</span> at a dye concentration of 12 mg/L, above which further increases in concentration yield little improvement. PIV correlation values remain robust up to 20 mg/L. The technique resolves surface features differing in amplitude by two orders of magnitude and is demonstrated on flow past a cylinder interacting with surface waves and on droplet impacts on a quiescent surface.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 9","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-026-04242-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148615049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Underbody ground vehicle aerodynamics with the Ring of Fire 车底地面车辆空气动力学与火环

IF 2.7 3区工程技术

Experiments in Fluids Pub Date : 2026-07-25 DOI: 10.1007/s00348-026-04284-1

Adrian Grille Guerra, Andrea Battegazzore, Coen Holland, Pablo Ignacio Alvarez Garcia, Andrea Sciacchitano

{"title":"Underbody ground vehicle aerodynamics with the Ring of Fire","authors":"Adrian Grille Guerra, Andrea Battegazzore, Coen Holland, Pablo Ignacio Alvarez Garcia, Andrea Sciacchitano","doi":"10.1007/s00348-026-04284-1","DOIUrl":"10.1007/s00348-026-04284-1","url":null,"abstract":"<div><p>This study presents an experimental investigation of ground vehicle underbody aerodynamics using the Ring of Fire (RoF) approach, enabling unprecedented quantitative three-dimensional flow visualizations. A novel facility is introduced where the Lagrangian particle tracking system is installed underground beneath a transparent floor, providing full optical access to the underbody region of moving vehicles. Helium-filled soap bubbles are employed as flow tracers in combination with high-speed imaging, LED illumination and the Shake-The-Box particle tracking algorithm to reconstruct the three-dimensional velocity fields. The methodology is first validated on a radio-controlled car equipped with interchangeable flat floor and diffuser configurations, with and without vortex generators. The results confirm that the diffuser induces significant flow acceleration and pressure reduction at its inlet, enhancing downforce, while vortex generators promote momentum exchange near the wall and suppress localized separation. Pressure fields reconstructed from the velocity data are consistent with known theory and literature on diffuser aerodynamics. The approach is subsequently applied to a full-scale open-wheel race car, demonstrating its capability to resolve complex three-dimensional flow structures under realistic operating conditions. Strong acceleration beneath the front wing and diffuser is observed, along with coherent vortical structures shed from flow control devices. The results highlight the potential of the RoF technique for detailed aerodynamic characterization and validation of high-performance vehicle designs in on-road conditions.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 9","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-026-04284-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148614108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Analytical models of focusing schlieren systems and experimental validation 聚焦纹影系统的分析模型及实验验证

IF 2.7 3区工程技术

Experiments in Fluids Pub Date : 2026-07-23 DOI: 10.1007/s00348-026-04245-8

Philip A. Lax, Sergey B. Leonov

引用次数: 0